Hi,
isn't sound in separate file with same name just with different extension? Supposing v in v264 means just video, but weird there isn't any duration. If audio is somehow encrypted, you can as last resort screencaptured V264Player output for example with OBS studio. Seems to be some proprietary AV file.

Ok, I found the player and hear the sound (someone knocking). It's some weird proprietary format/extension to H.264 ES. All slices seem to have some extra audio data. But I'm not qualified for reverse engineering so the best I could do would be to just old school record the audio output of the player... Good luck.